1. Field of the Invention
The present invention relates generally to a product isolation process for use in various carboxylic acid production processes. More specifically, the present invention concerns equipment and processes for isolating purified carboxylic acid particles from a slurry comprising an aliphatic acid.
2. Description of the Prior Art
In conventional terephthalic acid (TPA) production processes, para-xylene undergoes oxidation to form crude terephthalic acid (CTA) particles. A slurry of CTA particles can then undergo purification to form purified terephthalic acid (PTA) particles. A purified slurry comprising PTA particles and a liquid phase can then be treated in a product isolation zone to isolate at least a portion of the PTA particles. In some cases, the liquid phase of the purified slurry comprises oxidation byproducts formed from the oxidation of para-xylene.
Various techniques are known in the art for isolating PTA particles from a purified slurry. An example of one such technique includes the use of a vacuum filter. Vacuum filters typically employ a filter cloth through which the liquid phase of the slurry is drawn using a vacuum source, thus leaving a filter cake of PTA particles on the cloth. However, conventional techniques for isolating PTA can be problematic when the liquid phase of the purified slurry contains oxidation byproducts, due to the tendency of such oxidation byproducts to precipitate onto the filter cloth. Such precipitation can foul the filter cloth thereby reducing the filtration rate. Additionally, filter surfaces and conduits that the liquid phase contacts after exiting the filter cloth can also become coated with oxidation byproducts and eventually plug with solids. Accordingly, there is a need for methods and/or equipment that can reduce oxidation byproduct precipitation during PTA isolation.